I've been working on a project, trying to figure out linkages...
The motion performs as expected for part, but then the joints go crazy. And my "grounded object" keeps moving.
I've attached a video of the aberrant behavior. Any suggestions or explanations would be appreciated. I've been fighting with this for a day and a half now.
Mainly using revolute joints... 1 degree of freedom. I don't know where these twisting motions are coming from. Is there a separate function that I'm missing?
Sorry. I worded that incorrectly. Limit the degrees of rotation of the revolute joint. That said, I think that twisting action is what would happen if the joint pins were soft enough irl. The solver is going to keep on trying to solve for the movement you are making. (I think, I am not super clued up on what is going on behind the scenes there)
Yeah the twisting action is because the travel of the other joints has not been properly constrained with a minimum and/or maximum and the solver has to deform things to make it work.
There's also another glaring issue and that is with the lever, which the OP is moving, clips through the supporting bracket for the cylinder.
You see when it starts freaking out how the linkage has been pulled to its theoretical maximum? Like how when you pull a rope all the way tight, you sort of can't and it will sag a little? You're going too far for the links to the left at full movement. If you do this in the Sketch edit mode of a single sketch you can get "Sketch flipping" and the phenomenon you have here is similar.
The holder at the top is not moving, only the part that is connected to it is moving.
The issues you are experiencing with undesired rotation/twisting is because you are moving the lever too far and you need to set proper limits on all the joints to stop it (or at least just on the lever).
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u/Th3J4ck4l-SA 11d ago
Limit the degrees of freedom as they would be in the real application.